package com.linkai.注解和反射.reflect;

import java.lang.annotation.*;
import java.lang.reflect.Field;

/**
 * @Description: 练习反射操作注解
 * @Author: 林凯
 * @Date: 2021/10/21 20:07
 */
public class Test12 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
        Class<?> c1 = Class.forName("com.linkai.注解和反射.reflect.Student2");

        // 通过反射获得注解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation : annotations) {
            // @com.linkai.注解和反射.reflect.TableJackLin(value=db_student)
            System.out.println(annotation);
        }

        // 获取注解的 value 的值
        TableJackLin annotation = c1.getAnnotation(TableJackLin.class);
        System.out.println(annotation.value());     // db_student

        // 获得类指定的注解(先获得具体的属性，然后获取属性上的注解，然后 注解.xxx 就能获取值)
        Field name = c1.getDeclaredField("name");
        FieldJackLin annotation1 = name.getAnnotation(FieldJackLin.class);
        // @com.linkai.注解和反射.reflect.FieldJackLin(columnName=db_name, type=int, length=10)
        System.out.println(name.getAnnotation(FieldJackLin.class));
        System.out.println(annotation1.columnName());
        System.out.println(annotation1.length());
        System.out.println(annotation1.type());

    }
}

@TableJackLin("db_student")
class Student2 {

    @FieldJackLin(columnName = "db_id", type = "int", length = 10)
    private int id;

    @FieldJackLin(columnName = "db_age", type = "int", length = 10)
    private int age;

    @FieldJackLin(columnName = "db_name", type = "int", length = 10)
    private String name;

    @Override
    public String toString() {
        return "Student2{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }

    public Student2() {
    }

    public Student2(int id, int age, String name) {
        this.id = id;
        this.age = age;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

// 类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableJackLin {
    String value();
}

// 属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldJackLin {
    String columnName();
    String type();
    int length();
}
